Microwave plasmas are used in the industrial chemical processing of gases. This is typically accomplished by flowing the gases to be reacted through an elongated vessel while microwave energy is coupled into the vessel to generate a plasma. The plasma cracks the gas molecules into component species. Microwave chemical processing systems are effective because microwave plasmas operate at relatively high power coupling efficiencies at low ion energies, and are capable of supporting various gas reactions, such as the conversion of methane into hydrogen and carbon particulates, the conversion of carbon dioxide into oxygen and carbon, and coating particulates and other seed materials with other layers for functionalization and complex layered materials and aggregates processing.
Typical systems for chemical gas processing include a quartz reaction chamber through which process materials flow, and a microwave magnetron source coupled to the reaction chamber through a waveguide. The input microwave energy can be continuous wave or pulsed. Systems are designed to control the effective coupling of the microwave energy into the reaction chamber, and the gas flow within the reaction chamber to improve the energy absorption by the flowing gas. Often the systems include a wedge located where the microwave waveguide intersects the quartz reaction chamber, to concentrate the electric field within a small area, and the waveguide conductive walls are not exposed to the gases to be processed.